Fluid control valves include a housing having a fluid flow passage therein and a valving member that is movable relative to the housing to selectively block or open the fluid flow passage. The valving member is operatively connected to a valve stem which extends through the housing. A portion of the valve stem external of the prior art valve body is engaged by an actuator. Rotation of the actuator generates movement of the valving member to block or open the fluid flow passage.
Valve stems on certain prior art valves are threaded and engage threads in the actuator on the housing. Rotation of the actuator causes the valve stem to translate along its axis and relative to the valve housing. This axial translation of the valve stem generates the movement of the valving member to open or block the fluid flow passage in the prior art valve housing. In particular, a translation of the valve stem out of the valve housing will open the fluid flow passage. Conversely, a translation of the valve stem into the prior art valve housing will close the fluid flow passage. Prior art valves having a valve stem that translates relative to the valve housing often are referred to as rising stem valves.
One type of rising stem valve is a diaphragm valve. The valving member of a diaphragm valve is a flexible material, or diaphragm, that is selectively moved by the valve stem to regulate the size of an opening in the fluid flow passage from a fully closed position to a fully opened position. The diaphragm also functions to the separate the valve stem and other moving components of the valve from the flow of fluid. Diaphragm valves, therefore, are widely used in environments where the fluid flowing through the valve is particularly corrosive or abrasive and is likely to damage the operative components of the valve. The valve stem of a prior art diaphragm valve extends from the diaphragm and through the valve housing. A portion of the valve stem intermediate its length includes an array of external threads. The prior art diaphragm valve further includes an actuator, such as a hand wheel. The prior art actuator typically includes an array of internal threads which threadedly engaged stem. In this typical prior art diaphragm valve, the actuator is rotatable relative to the housing, but is axially fixed in the housing relative to the axis of rotation of the actuator. Consequently, rotation of the actuator causes the prior art valve stem to translate along its axis.
The amount of translation for each rotation of the actuator in the prior art diaphragm valve is determined by the pitch of the thread on the valve stem. In some instances several rotations of the actuator are required to translate the valve stem sufficiently to move the diaphragm from the fully closed position to the fully opened position. The relative position of the diaphragm in the prior art diaphragm valve is not readily visually detectable in the prior art valve. In particular, it is difficult to determine whether the prior art diaphragm valve is in a fully closed position, a fully opened position or some position therebetween. In view of this inherent problem, prior art diaphragm valves often are provided with a sight glass which encloses the end of the valve stem external of the valve housing. The sight glass is provided with graduated markings which are intended to correspond to the relative axial position of the valve stem. Thus, a technician can visually align the axial end of the valve stem with the graduated markings on the sight glass to determine whether the diaphragm is in the fully open position, the fully closed position or some position therebetween.
The graduated sight glass on prior art diaphragm valves include several short comings. First, sight glasses are very difficult to observe from any significant distance. Second, the interpretation of the sight glass readings vary significantly in accordance with the angle of viewing. Third, the sight glass can become soiled after even a short period of use in an industrial facility, thereby making any reading virtually impossible. Fourth, it often is undesirable or unsafe for technicians to be moving into close proximity to the valve for making the visual inspection of the sight glass. In this latter regard, the need to periodically inspect a sight glass to check a relative position of a valve often can offset the efficiencies that can be achieved with automatic valve actuators.
The prior art includes several other types of rising stem valves that suffer from the same deficiencies. For example, some gate valves include a rising stem. A gate valve includes a valving member that is a generally planar disk or plate that can be moved in its plane into our out of the fluid flow passage of the valve housing. The plate or valve disk may be fixedly mounted to one end of a valve stem. A hand wheel or other such actuator similar to that described for the diaphragm valve may be mounted external of the valve housing and threadedly engaged with the valve stem. Rising stem gate valves suffer from the same inefficiencies as the above described rising stem diaphragm valves in that the relative position of the valving member cannot easily be determined.
Some prior art globe valves also include a rising stem. These prior art rising stem globe valves also suffer from the same inefficiencies as the above described prior art diaphragm valve in that the relative position of the globe valving member cannot readily be visually determined.
In view of the above, it is an object of the subject invention to enable an efficient determination of the relative position of the valve member in a rising stem valve.
It is another object of the subject invention to provide a position indicator for a rising stem valve that enables accurate determination of the valving member position from a remote location.
It is another object of the subject invention to provide a position indicator for a rising stem valve that can be adapted to different size valves.
Still another object of the subject invention is to provide a position indicator for a rising stem valve that avoids the need to employ a graduated sight glass.